Solid-oxide fuel cell system and method of stopping same
A solid-oxide fuel cell system includes: a fuel cell unit including a solid-oxide fuel cell including an anode gas channel and a cathode gas channel and a mixer; an electric power generation raw material supplier; a combustible gas channel extending from the electric power generation raw material supplier to a downstream end of the anode gas channel; an oxidizing gas supplier; and a controller operative to, after electric power generation of the fuel cell unit is stopped, control the electric power generation raw material supplier to supply to the combustible gas channel the electric power generation raw material, the amount of which compensates for contraction of gas in the combustible gas channel due to temperature decrease of the fuel cell unit and also control the oxidizing gas supplier to supply the oxidizing gas to the cathode gas channel in accordance with the supply of the electric power generation raw material.
1. A solid-oxide fuel cell system comprising:
a fuel cell unit including
a solid-oxide fuel cell including an anode gas channel and a cathode gas channel and
a mixer operative to mix an anode off gas discharged from the anode gas channel and a cathode off gas discharged from the cathode gas channel;
an electric power generation raw material supplier operative to supply an electric power generation raw material to the fuel cell unit;
a combustible gas channel extending from the electric power generation raw material supplier to a downstream end of the anode gas channel;
an oxidizing gas supplier operative to supply an oxidizing gas to the cathode gas channel; and
a controller operative to, after electric power generation of the fuel cell unit is stopped, control the electric power generation raw material supplier to supply to the combustible gas channel the electric power generation raw material, the amount of which compensates for contraction of a gas in the combustible gas channel due to temperature decrease of the fuel cell unit and also control the oxidizing gas supplier to supply the oxidizing gas to the cathode gas channel in accordance with the supply of the electric power generation raw material.
2. The solid-oxide fuel cell system according to claim 1 , wherein after the electric power generation of the fuel cell unit is stopped, the controller controls the electric power generation raw material supplier and the oxidizing gas supplier to intermittently supply the electric power generation raw material and the oxidizing gas.
3. The solid-oxide fuel cell system according to claim 1 , wherein after the electric power generation of the fuel cell unit is stopped, the mixer mixes the oxidizing gas and the electric power generation raw material, and the controller controls the electric power generation raw material supplier or the oxidizing gas supplier such that an amount of electric power generation raw material supplied becomes an amount by which a concentration of the electric power generation raw material in the mixer is outside a combustible range.
4. The solid-oxide fuel cell system according to claim 1 , wherein after the electric power generation of the fuel cell unit is stopped, the controller controls the electric power generation raw material supplier such that a volume of the electric power generation raw material supplied to the combustible gas channel becomes not more than a volume of the combustible gas channel.
5. The solid-oxide fuel cell system according to claim 4 , wherein the controller controls the oxidizing gas supplier such that a volume of the oxidizing gas supplied to the cathode gas channel after the electric power generation of the fuel cell unit is stopped becomes not less than a volume of the cathode gas channel.
6. The solid-oxide fuel cell system according to claim 4 , wherein the controller controls the oxidizing gas supplier to keep on supplying the oxidizing gas to the cathode gas channel even after the supply of the electric power generation raw material to the combustible gas channel is stopped after the electric power generation of the fuel cell unit is stopped.
7. The solid-oxide fuel cell system according to claim 1 , wherein the fuel cell unit includes a hydro-desulfurizer operative to remove a sulfur compound in the electric power generation raw material supplied from the electric power generation raw material supplier.
8. A method of stopping a solid-oxide fuel cell system,
the method comprising the steps of:
stopping electric power generation of a fuel cell unit including a solid-oxide fuel cell; and
when a channel extending from an electric power generation raw material supplier to a downstream end of an anode gas channel of the solid-oxide fuel cell is a combustible gas channel and after electric power generation of the fuel cell unit is stopped, supplying to the combustible gas channel an electric power generation raw material, the amount of which compensates for contraction of a gas in the combustible gas channel due to temperature decrease of the fuel cell unit and also supplying an oxidizing gas to a cathode gas channel of the solid-oxide fuel cell in accordance with the supply of the electric power generation raw material.